don't use light novel spoilers for explanation on the latest episode.
The butei students are covered with bullet proof when they enter 2nd year. So aside from a hit from the head then the chances of death isn't that high but still there are chances. And when you enrolled in butei high then you should be responsible for your life. It's an institution of armed detectives to begin with.
Though Aria's action is pretty childish just from the word Love. But that's her character. Plus there are reasons from it but just I say no reasoning using novel so I can't answer that aside that it's a tsunderes act.